Question
$\text{if y} =\text{x}^{x},\text{prove that } \frac{\text{d}^{2}\text{y}}{\text{dx}^{2}} -\frac{1}{\text{y}}\bigg(\frac{\text{dy}}{\text{dx}}\bigg)^{2} -\frac{\text{y}}{\text{x}} =0.$

Answer

$\text{y} = \text{x}^{\text{x}}\therefore\log\text{ y } =\text{x}\log\text{x},$
Taking log of both sides
$\Rightarrow\frac{1}{\text{y}}\frac{\text{dy}}{\text{dx}} =\log\text{x} + 1 ,$
Diff. w r t “x”
$\Rightarrow\frac{1}{\text{y}}\frac{\text{d}^{2}\text{y}}{\text{dx}^{2}} -\frac{1}{\text{y}^{2}}\bigg(\frac{\text{dy}}{\text{dx}}\bigg)^{2} = \frac{1}{\text{x}},$
Diff. w r t “x”
$\Rightarrow\frac{\text{d}^{2}\text{y}}{\text{dx}^{2}} -\frac{1}{\text{y}}\bigg(\frac{\text{dy}}{\text{dx}}\bigg)^{2} - \frac{\text{y}}{\text{x}} - 0 .$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free